Spark-plug.



PATENTED DEG. 18, 1906.

R. O. HOOD.

SPARK PLUG.

APFLICATION FILED M19, i904.

a. www? fir/vv a les RALPH O. HO0D UF DANVERS, MASSUHUST @ii UNE-HALF TU WARREN D. liilGf GF EABBY, MASSACHUSETTS.

No. 538.994v

Speeieetion of Letters Patent.

secliusetts, lieve invented eeertein new and useful improvement in Sporioilugs, of which the following is e specification, referenee be in had therein to tile accompanying drewing.

/lv invention lies for its object to provide an improved spark-plug for gesolene-engines and the like.

My spark-plug is so arranged tliet it may be reed ily removed es e Whole whenever it is necessary to olefin it or to examine the speri;- ing points. .Tt is also so devised that pen feet insulation of, the various parts is ineinteined under ell conditions of temperature.

The invention Will loe readily understood from the following description., in which reference is mede to. the accompanying drewing, and the novel features thereof ere pointed out, end clearly defined in the claims et the elose of this specification.

The Adrawing 'showen spark-plug embodying my invention, partly in vertical section and partly in elevation.

Referring to the drawin', A represents e portion of the engine-eylinner into which the spark-plug is screwed, es shown et l. The exterior cylindrical easing', which surrounds and protects the interior portions of spark-plug, is shown et 2. Within this casing end insulated freni it in manner llereinefter more particularly described is s stein 7, provided with e heed et its lower end. The easing 2 is of e gres-ter diem-eter outside the cylinder end is preferably provided with e shoulder 3, which beers against the e3;- terior of the engine-cylinder when the spariplng is screwed ironie. Tle threaded portion of the sperloplug eos' somewhat less diameter7 ss sli( the lowl l i of t g, i:

end below t. f i.

,ss diemk Y et the en 1^ t1i spark-plug cesin Le portion e a point or lip 5 is provided Whi ,l1 is lient ines shown et e.

wardly, es shown7 le* fing s sinell space or breek between sti-d lip and the lneod or lov/'ei` end 6 of tnestein Woo spark, 1oy ineens of 'which the end ges in the engine-cylinder formed by the passage the e f f eeross the space between tire poni o t 'eetion 5 and the need of thestezn 7.

will be nnderstooilbY those skilled in the srt the stern 7 end tile cesing ere conneeted electrically in any Well-known *sonner with e proper source ol electric The spark-plug easing 2 is longitndinel oper ing' there ,n ception of tile stern. 7 i suletion. Tire openin (shown et li) is contre ing e shoulder et l. rounding the stern from laminated mice in tl The stein 7 shove the heed id or sovered with sheets of inice/lsiiown et which ere Wrapped about the stern. Qetside oi' tliisniice wrapping i) end immedietely sbo-ve 7 the heed 6 of the stem 7 is series of Woshers of mice, which ore superimposed pressed together, The lowerniost series Aoi' tiiese washers is shown et il) end is of snlostentielly the die-meter et' the heed Goi tiiestern 7i 7 which diameter is less then the interior oi' tile surrounding portion et of the rinsing, time iording en 'r-speee outside of tire Washers ecross Wliic spark is proies" Above the series of vri l l is smother 8 series 8, which ere oi e diameter equa-l to the interior diameter or bore of the easing 2 end till the space between niioe wrapping 9 about the stein 27 sind tne interior well of the seid casing These e'esl ors S also press 8 firmly eerinst the shoulder 1 es will be later erpl ed, and prevent about the. spark-plee ir of the cylinder. Next itoer-re Washers is :mother series of ,vesliers i3 of e Adiameter semen/'liet less than tlie dienieter of the contre-ted portion of 'die Above this series ol mice Washers i2 is e, fourth series l5 of sin i sliers of zi olemeter greater t r ol the e eontreetel in prec! tice l molle l :7" seme di- @meter es 1li`Vr vui' lie series making the i i s diemetertlien the. two edjee nt s Ad en annuler groove, sniteilileiior option or" the contracted portion of li @sing 2,is formed in tlie lio/dy or" insuletion. The series of Washers etend opvfrdlj/ le e nietel disk or vv lslier l?? fn Yetonne which I this disk is placed e-iove the upper edge of tlie casino; 2 being determined l the length oi tne stein 7 end Vtix i other ports oi the deviee.

'ilie leyeroifinsslitting-washers i3 may, it" i surface of the casing Z and the washer 16, while the layers 8 and 10 are compressed be' tween the shoulder i2 and the head 6 of the stem 7 but in practice i prefer to employ a layer l13 of such .thickness that the whole 'niass oi insulation will be compressed between the washer 16 and the head 6, aswell lIc' as against the upper and lo'wer surfaces of' the cbht'racted portion 12 'of `the Casin 2. This may be easily accomplished by ad ing Washers to the'flayer 13 one at a time until the right' thickness is obtained. The whole is'lorined into a solid body firmly united to the casing?y and linsures electrical insulation oi the parts without danger of leakage of glass- The stem 7 is made smaller in diameter, as 'shownat '7,;ior a portion of its length which is'opposite the-oontractedopening 11 at the top' oit-the casing 2, thereby increasing the distance between the said stem and the proxi- I matetvall or portion of the top of the casing 2 and increasing the. insulation at this point,

'wherethere is" ieat danger of leakage.

14llil'acare the disk 16 the stem 7 is surrounded for a considerable plortion of itslength by a cylinder or sleeve "i8, the upper end of which rests againsta head 'or nut 20, threaded. upon the stem 7. There fis also provided archecli-niit 21 for' additional security. By

screwing ldown the nut 20 lthe insulatingwashers composing the body 'of insulation about the-stem 7 and within thescasing 2 .are

firmly compressed, it'being possiblev to apply grefpressure, so` that the insulation 1s 'as completely solidified as possible.

A'illiesl'eeve 18 is preferably made of brass or lothernietal having a coeilicientv of expansijcn greater than that, of the stem 7, the stem 7 being* preferably made of iron or steel. By making thel sleeve 18 of a proper length with reifatic'n tothe length of the stem 7, which has a less coefficient of expansion, the total expansion of the sleeve 18 and the stern 7 may be made almost exactly the saine, 4'so that the washers composing the body of insulatinr'i about the stern are subjected to a conn starrt' pressure regardless of the temperature to which the spark-plug is exposed. This is particularly desirable, since sparlr-plugs for use in eXplo'sion-engines -are subjected to very'great variations in temperature and it has been found'diflicult to provide insulation for the 'parts' of the sparl -plu`gs which shall be unaffected by the changes in length of the diiierent parts. l

By the employment 4of my-invention a very durable' sparleplug inwhich the stem is at: all times maintained in complete insulation from the' casin is obtained at a minip mum'of eXp-ense'.l The .construction also insures great uniformity in the' expansion of assess stem provided with heads at both ends, a

sleeve about the said stem, insulation be tween one end of the sleeve and the correspondinghe'ad oll the stem, and a casing about the said insulation and having a shoulder engaging a corresponding groove in the body of insulation and forming a gas-tight joint therewith.

' 2'.' in a spark-plug, the combination oi a casing provided with an interior shoulder, a stem provided with heads at both ends, insulation about the said stem'and between one of its heads and the shoulder of the said casing, a sleeve about the said stem and `abutting'vagainst its other head, and insulation between theend of the sleeve and the exterior of the casing.

3. In a spark-plug, the combination oli a casing' provided with an interior shoulder, a

stem provided with heads at both-ends and a contractedportion at a point about op osite the'said shoulder on the stem, insu ation about the said stem and between one of its Aheadsand the shoulder of the said'ca'sing, a .sleeve about th said stem and abutting against its other head andV insulation between the end 'of the sleeve andthe exterior ofthe casing.

4. In a spark-plug, the combination of a stem provided with heads at both ends, a sleeve about 'the said stem, made of metal having a greater coefficient of expansion than `the said stem and proportioned in length vto have an expansion substantially equal to that of the'stem, insulation between one end of the sleeve and the corrcspcndin head ofthe stem, and a' casingl about the saidl insulation andhaving a shoulder engagin a corresponding groove in the body oi' insul ation and forming a gas-tight joint therewith.

5. In a spark-plug, the combination'of a casing provided with an interior shoulder, a stem provided with heads at both ends, insulation about the saidv stem and between one of its heads andthe shoulder of the said casing, a sleeve about the said stern and'abutting against 'its other head, said sleeve bei-ng made of metal having a greater coefficient' of expansion than the said stem and proportioned in length to have an expansion sub -stantially equal tothat of the stem, and insu lation between the ond of the sleeve and the exterior of the casing.

A In testimonyY whereof l arhx my signature in presence ol' two witnesses.

RALPH o, Hoon.

`l/Vitnesses z' GEORGE` P. Duin, WILLIAM A. CoPELANo, 

